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Acquired platelet dysfunction, which is common, may result from aspirin, other NSAIDs, or systemic disorders.
Acquired abnormalities of platelet function are very common. Causes include
Acquired platelet dysfunction is suspected and diagnosed when an isolated prolongation of bleeding time is observed and other possible diagnoses have been eliminated. Platelet aggregation studies are unnecessary.
Drugs:
Aspirin and other NSAIDs, which are very commonly used drugs, may induce platelet dysfunction. Sometimes this effect is incidental (eg, when the drugs are used to relieve pain and inflammation) and sometimes therapeutic (eg, when aspirin is used for prevention of stroke or coronary thrombosis). Other therapeutic antiplatelet drugs include clopidogrel, ticlopidine, and the glycoprotein IIb/IIIa inhibitors.
Aspirin and NSAIDs prevent cyclooxygenase-mediated production of thromboxane A2. This effect can last 5 to 7 days. Aspirin modestly prolongs bleeding time in healthy people but may markedly prolong bleeding time in patients with underlying platelet dysfunction or a severe coagulation disturbance (eg, patients receiving heparin, patients with severe hemophilia).
Systemic disorders:
Many disorders (eg, myeloproliferative and myelodysplastic disorders, uremia, macroglobulinemia and multiple myeloma, cirrhosis, SLE) can impair platelet function.
Uremia may prolong bleeding via unknown mechanisms. If bleeding is observed clinically, bleeding time may be corrected transiently with vigorous dialysis, cryoprecipitate administration, or desmopressin infusion. If indicated for treatment of anemia, RBC count can be increased by transfusion or by giving erythropoietin; this process also shortens the bleeding time.
Cardiopulmonary bypass:
Platelets may become dysfunctional, prolonging the bleeding time as blood circulates through a pump oxygenator during cardiopulmonary bypass. The mechanism appears to be activation of fibrinolysis on the platelet surface with resultant loss of the glycoprotein Ib-IX binding site for von Willebrand's factor. Regardless of platelet count, patients who bleed excessively after cardiopulmonary bypass and who have a long bleeding time are transfused with platelets. Giving aprotinin (a protease inhibitor that neutralizes plasmin activity) during bypass may preserve platelet function, prevent prolongation of bleeding time, and reduce the need for transfusion.
Last full review/revision May 2009 by James N. George, MD
Content last modified May 2009
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